This application relates in general to the same subject matter as is disclosed in my patent application for a Torque Converter Mechanism Ser. No. 96,653, filed on even date with this application. Specifically, application Ser. No. 96,653 discloses a two-range torque converter together with means for locking the impeller element of the converter to the turbine element thereof to obtain a direct or lock-up drive between the impeller and the turbine when the converter would otherwise be operating as a fluid coupling.
This application discloses an alternate means for locking the impeller to the turbine but is not concerned with the two-range feature disclosed in the above-identified application. This application also discloses means for reducing the torque transmitted by the converter when the engine is idling with the transmission in gear.
The power transmitted by the conventional vehicle torque converter varies roughly as the cube of the impeller speed. Thus, a converter which will transmit 100 H.P. at 2000 r.p.m. impeller speed will transmit about 5 H.P. at 500 r.p.m., the idling speed of the conventional automobile engine. Consequently, when a vehicle equipped with such converter is brought to a stop with the engine idling and the transmission in gear, the converter will still exert a driving force of about 5 H.P. At such time the converter's turbine is, of course, stationary with the vehicle transmission in low or starting gear so that the driving torque of the turbine is amplified by both the turbine's stator and the vehicle transmission. This results in a torque buildup of about 200 ft pounds on the vehicle propeller shaft. This torque is, of course, more if the engine is on fast idle as occurs for some time during engine warm up.
With my improved converter the turbine torque is not eliminated under idling conditions but the torque due to the converter buildup is eliminated and the torque generated by the fluid coupling effect is reduced so that the driving force on the propeller shaft when the engine is idling is less than half that of an equivalent size conventional converter.
In the normal operation of a motor vehicle the constantly applied driving force at engine idling speed is partly resisted by the rolling resistance of the vehicle but in most automobiles the rolling resistance is not sufficient to prevent the vehicle from moving. Consequently, to prevent such movement of the vehicle, the vehicle brakes must be continuously applied or the transmission shifted out of gear.
This characteristic of vehicle torque converters has long been recognized as a safety hazzard. For example, where such a vehicle is stopped for a traffic signal and the driver, thru error or because of distractions from any source, momentarily releases the brake pressure the vehicle immediately starts to move forwardly into the cross traffic and often will cause a collision with another vehicle which has the right of way.
With my improved converter, even through the power transmitted at idling speed of the engine is not reduced to zero, it is reduced sufficiently that the normal rolling resistance of the vehicle will prevent the vehicle from moving after it has once been stopped. Consequently, the brakes of the vehicle need not be continuously applied to keep it from moving forwardly.
A further advantage of my converter is that the engine, when idling, need develope less than half of its normal power so that a substantial saving in fuel results.